The present invention relates to a particle agglutination immunoassay apparatus employing a method of measuring particle sizes of agglutinated microparticles. More specifically, the invention relates to a particle agglutination immunoassay apparatus adapted to a determination method by applying the immunoagglutination reaction.
A method has heretofore been proposed according to which an antibody is coupled to the surfaces of microparticles such as latex beads and is reacted with a specimen to measure the amount of antigen in the specimen relying upon a difference in turbidity that changes depending upon the reaction. The principle is based upon the fact that the antigen on the surfaces of microparticles takes part in the antigen-antibody coupling reaction to agglutinate the microparticles and that the agglutination changes quantitative by with respect to the amount of the antigen. A variety of proteins have been determined based upon this method. With this method which measures at one time the whole reaction liquid having distribution in the agglutination degree, however, the average diameter only could be found leaving a problem with regard to precision for calculating the antigen concentration.
In order to solve this problem, there has been proposed a method in which the reaction liquid is dispersed for each agglutinated mass by the sheath flow method to measure the scattering intensity (journal of the Japanese Association of Automated Clinical Examination, 11, 1986, p. 226). According to this method, the agglutination degree of each of the agglutinated masses can be measured and the distribution of agglutination degrees can be measured, too, making it possible to improve the precision for calculating the antigen concentration.
Even in this method, however, the agglutination degree is measured in an optical manner and is inevitably affected by matters scattered in the specimen and absorbant such as pigment, imposing limitation on the measuring precision.
According to the above-mentioned prior art, no attention has been given to the effects caused by the matters scattered in the specimen, absorbant such as pigment or fluorescent material, giving rise to the occurrence of error in the measurement.